Hydraulic jack of follow-up type



1953 R. LUCIEN 3,108,512

HYDRAULIC JACK OF FOLLOW-UP TYPE Filed April 24, 1962 2 Sheets-Sheet 1 FIG.1

Oct 29, 1963 R. LUCIEN 3,108,512

HYDRAULIC JACK 0F FOLLOW-UP TYPE Filed April 24, ,1962 2 sheets-sheet 2 as 24' I6 7 FIG.3

United States Patent 3,108,512 HYDRAULTC JAEK 8F FULLGW-UP TYPE Rene Lucien, Neuiliy-sur-Eieine, France, assignor to Socie't a Rcsponsabilit Liinite: Recherehes Etudes Production R.E.P., Paris, France, a corporation of France Filed Apr. 24, 1962, Ser. No. 189,803 4 Claims. (Cl. 91-216) The invention relates to a hydraulic jack of the followup control type, working on a hydraulic pressure unit of the so-called closed centre type.

In this kind of hydraulic servo-control, it is necessary to reduce the internal leakages of liquid to the maximum possible extent and, as far as this can be achieved, to eliminate them from the interior of the distribution valve.

The servo-control according to the invention complies with these fundamental requirements.

It is characterized in that its moving member, actuated by the manual effort to be transmitted by servo-control, is constituted by a fiat slide-valve which moves between the flat surfaces of two slide-faces in contact with said slide-valve, and comprises three transverse channels which pass right through it and which ensure the distribution or" the liquid under pressure, in the following conditions:

(a) The central channel maintains a permanent communication between two chambers formed in the said slide-faces and of which one is coupled to the source of fluid under pressure.

(b) On the same edge of the fiat slide-valve, on the incoming pressure side, the two lateral channels terminate in two cavities which, when the slide-valve is driven in one direction or in the opposite direction, alternately put one of the chambers of the jack in communication with the incoming pressure side and the other chamber is put to exhaust, by virtue of the presence of two opposite cavities belonging respectively to the said slide-faces.

(c) On the opposite edge of the flat slide-valve, these same lateral channels open into two further cavities formed in the slide-face which is located on the side opposite to the arrival of the pressure fluid.

Furt er characteristic features of this follow-up control will become apparent from the following detailed description with reference to the accompanying drawings.

In these drawings:

FIG. 1 is a longitudinal section of the device taken along the axis of the jack.

FIG. 2 is a partial view on a larger scale.

HS. 3 is a transverse section taken along the line Iiilll of FIG. 1.

in the drawings, the body of the jack is shown at 1 and its piston at 2. it will be assumed, for example, that the stationary point of the servo-control is at 3ton the piston rod, and that it is the whole of the body 1 which is compelled to move in the direction of the arrows f F, depending on the action of the manual drive which is applied through the intermediary of the lever 4 on the flat slide-valve T.

In accordance with the invention, this slide-valve moves between two opposite cylindrical slide-faces G and G the flat bases of which are in contact with the slide-valve. A spring 5 ensures the centering of the slide-valve with respect to the slide-faces. 7

Two further springs 6 and 7 apply the slide-faces against the slide-valve, and ensure fluid-tightness within the interior of the servojack when starting-up under pressure.

The slide-valve is traversed by two channels 8 and 9, located on either side of a central channel 1%.

in the position of rest, this central channel is located opposite cavities it and 12 formed in the slide-faces, and

'ice

into which open two channels 13 and 14 which deliver into two chambers 15 and 16 respectively, in which are housed the springs 6 and 7 referred to above. The arrival P of the liquid under pressure is coupled to one of these chambers, in this case 15.

The lateral channels 8 and 9 terminate, on the side closest to chamber 15, in the two cavities 17 and 18.

When at rest, the chamber 17 covers the opening of a channel 19 formed in the slide-face G and communicating permanently with the chamber 2b of the jack.

On the opposite edge of the flat side-valve, the channels 3 and 9 open respectively into cavities 21 and 22 of the slide-face G and of which one, 22, is extended by a channel 23 communicating via groove 24 and conduit 25 with the other chamber 26 of the jack.

The return to the tank is connected to the orifice 27 coupled by channel 28 to the annular space 29. The operation of this hydraulic follow-up servo-control is effected as follows:

When the manually-operated swivel-jointed lever 4 urges the slide-valve T in the direction of the arrow the pressure coming from 15 is admitted to the chamber 20 of the jack along the path 13--11l719.

At the same time, the chamber 25 of the jack is put to the return to the tank at 27 over the path 25-2423-- 2291-8-2928.

The body 1 of the jack is thus displaced, under servoccntrol, in the direction f Conversely, when the lever 4 acts on the slide-valve T in the direction of the arrow 1 the pressure coming from 15 is admitted to the chamber 26 of the jack over the circuit 13-ld139222324-2 5.

At the same time, the chamber 28} of the jack is connected to the return to the tank at 27 by 1l7, the annular space 29 and the conduit 28.

The body 1 of the jack is therefore moved under servocontrol, in the direction F.

It can readily be seen that in both the directions and P, the control is effectively a follow-up, since any forward movement of the body 1 and with it of the slidefaces G and G tends to cut'ofi the communicationfrom the cavities to the channel-which had initiated the said forward movement.

It should be observed that the spring 5 determines the threshold effort necessary in order that the operator can feel the servo-mechanism.

Similarly, it is necessary during the control operation that the operator should feel a restoring force proportional to the outward force which is applied to the jack. It is for that purpose that two restoring chambers are formed at St? and 31. A force is applied by the pressure acting on the difierence in cross-sections: d a' for the chamber 30, and d d for the chamber 31. The chamber 3% creates a restoring force when the pressure is admitted to the annular chamber 26 of the jack. The chamber 31 creates this force when the pressure is admitted to the full section of the jack in the chamber 20.

It should also be noted that the pressure of the liquid arriving at 15 acts continuously and simultaneously on the slide-faces, thus preventing them from moving away from the flat slide-valve. The pressure acts on the annular sections (r)=(d d for the slide-face G and (s) =(cl d for the slide-face G To this action of the pressure, there is of course added the force applied by the springs 6 and 7.

Finally, in accordance with an advantageous feature of this servo-control, in order to prevent the slide-faces from becoming detached from the slide-valve during the successive phases of the distribution, a so-called compensating section is provided on each of the slide- 3 faces: namely, 32=(d d on the slide-face G and 33=(d d for the slide-face G These sections are in fact subjected to the pressure of that of the chambers of the jack which is supplied during the distribution phase in force, which has the result of increasing the force which applies the slide-face concerned against the fiat distribution slide-valve.

What I claim is:

1. A hydraulic jack comprising first and second bodies adapted to move relative to one another, a slide valve slidably supported in one of said bodies, slide faces in said one body past which said slide valve is adapted to move, said slide valve being provided with a central passageway and two lateral passageways extending therethrough, a pair of chambers, one being provided in each of said slide faces, one of said chambers being adapted for being placed into communication with a pressure fluid source, said chambers being permanently placed into communication with one another via said central passageway of the slide valve, said slide valve having surfaces respectively in contact with the slide faces, said slide valve in the surface thereof closer to said chamber which is in communication with the pressure fluid source being provided with a pair of cavities opening into said lateral I passageways, the slide face in contact with the surface of the slide valve which is remote from the chamber which is in communication with the pressure fluid source being provided with cavities which open into said lateral passageways, said bodies defining respective first and second chambers which when selectively furnished with pressure fiuid provide for opposite directions of relative movement of the bodies, means permanently establishing communication between one of the chambers defined by said bodies and one of the cavities in the slide face, means permanently establishing communication between the other of the chambers defined by said bodies and the cavity in the slide valve which communicates with the lateral passage which is in communication with the other of the cavities in the slide face, said slide valve and said one body defining an annular space surrounding that slide face in which is provided the chamber which is in communication with the pressure fluid source, said cavities in the slide valve being dimensioned to be isolated from the chamber provided in the associated slide face, with the slide valve in a neutral position, said cavities being respectively placed into communication with the latter mentioned chamber when the slide valve is moved in opposite directions, the direction of relative movement between the bodies being determined thereby.

2. A jack as claimed in claim 1, wherein said surfaces of the slide valve which are in contact with the slide faces are flat surfaces and the slide faces have mutually fiat surfaces.

3. A jack as claimed in claim 1, wherein both said means which establish respectively communication between said chambers defined by the body and the cavities in the slide valve and the slide face are each provided with a restoring chamber, each of the restoring chambers being formed along different cross-sections of the slide valve to exert a force on the slide valve resisting displacement thereof when pressure fluid is furnished to the respective chamber defined by the bodies as a result of movement of the slide valve.

4. A jack as claimed in claim 1, wherein both said means which establish respectively communication between said chambers defined by the body and the cavities in the slide valve and the slide face are each provided with a compensating chamber which is bounded by a respective surface of a slide face such that with pressure fluid furnished to the compensating chambers forces are developed on said slide faces urging the latter against said slide valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,218 Noll et a1 Apr. 18, 1950 2,676,663 Smith Apr. 27, 1954 2,757,743 MacDuff Aug. 7, 1956 2,916,016 Finvold Dec. 8, 1959 3,045,651 junggren July 24, 1962 

1. A HYDRAULIC JACK COMPRISING FIRST AND SECOND BODIES ADAPTED TO MOVE RELATIVE TO ONE ANOTHER, A SLIDE VALVE SLIDABLY SUPPORTED IN ONE OF SAID BODIES, SLIDE FACES IN SAID ONE BODY PAST WHICH SAID SLIDE VALVE IS ADAPTED TO MOVE, SAID SLIDE VALVE BEING PROVIDED WITH A CENTRAL PASSAGEWAY AND TWO LATERAL PASSAGEWAYS EXTENDING THERETHROUGH, A PAIR OF CHAMBERS, ONE BEING PROVIDED IN EACH OF SAID SLIDE FACES, ONE OF SAID CHAMBERS BEING ADAPTED FOR BEING PLACED INTO COMMUNICATION WITH A PRESSURE FLUID SOURE, SAID CHAMBERS BEING PERMANENTLY PLACED INTO COMMUNICATION WITH ONE ANOTHER VIA SAID CENTRAL PASSAGEWAY OF THE SLIDE VALVE, SAID SLIDE VALVE HAVING SURFACES RESPECTIVELY IN CONTACT WITH THE SLIDE FACES, SAID SLIDE VALVE IN THE SURFACE THEREOF CLOSER TO SAID CHAMBER WHICH IS IN COMMUNICATION WITH THE PRESSURE FLUID SOURCE BEING PROVIDED WITH A PAIR OF CAVITIES OPENING INTO SAID LATERAL PASSAGEWAYS, THE SLIDE FACE IN CONTACT WITH THE SURFACE OF THE SLIDE VALVE WHICH IS REMOTE FROM THE CHAMBER WHICH IS INCOMMUNICATION WITH THE PRESSURE FLUID SOURCE BEING PROVIDED WITH CAVITIES WHICH OPEN INTO SAID LATERAL PASSAGEWAYS, SAID BODIES DEFINING RESPECTIVE FIRST AND SECOND CHAMBERS WHICH WHEN SELECTIVELY FURNISHED WITH PRESSURE FLUID PROVIDE FOR OPPOSITE DIRECTIONS OF RELATIVE MOVEMENT OF THE BODIES, MEANS PERMANENTLY ESTABLISHING COMMUNICATION BETWEEN ONE OF THE CHAMBERS DEFINED BY SAID BODIES AND ONE OF THE CAVITIES IN THE SLIDE FACE, MEANS PERMANENTLY ESTABLISHING COMMUNCATION BETWEEN THE OTHER OF THE CHAMBERS DEFINED BY SAID BODIES AND THE CAVITY IN THE SLIDE VALVE WHICH COMMUNICATES WITH THE LATERAL PASSAGE WHICH IS IN COMMUNIATION WITH THE OTHER OF THE CAVITIES IN THE SLIDE FACE, SAID SLIDE VALVE AND SAID ONE BODY DEFINING AN ANNULAR SPACE SURROUNDING THAT SLIDE FACE IN WHICH IS PROVIDED THE CHAMBER WHICH IS IN COMMUNICATION WITH THE PRESSURE FLUID SOURCE, SAID CAVITIES IN THE SLIDE VALVE BEING DIMENSIONED TO BE ISOLOTED FROM THE CHAMBER PROVIDED IN THE ASSOCIATED SLIDE FACE, WITH THE SLIDE VALVE IN A NEUTRAL POSTION, SAID CAVITIES BEING RESPECTIVELY PLACED INTO COMMUNICATION WITH THE LATTER MENTIONED CHAMBER WHEN THE SLIDE VALVE IS MOVED IN OPPOSITE DIRECTIONS, THE DIRECTION OF RELATIVE MOVEMENT BETWEEN THE BODIES BEING DETERMINED THEREBY. 